Conventionally, for image forming devices, such as printers, photocopy machines, facsimile machines, multifunction machines and the like, an exposure device, such as an LED head or the like, used in printers, for example, exposes a charged photosensitive drum by irradiating light thereto and forms an electrostatic latent image on the photosensitive drum. A conventional exposure device includes a lens holder, a substrate on which an LED array is mounted by being held by the lens holder, a rod lens array that is held by the lens holder so as to face the LED array and that causes the light irradiated from the LED array to converge. The electrostatic latent image is formed as the light irradiated from the LED array mounted on the substrate converges through the rod lens array and exposes the photosensitive drum arranged at an image forming position of the rod lens array (see, for example, Japanese Laid-Open Patent Application No. 2010-64426 (pages 3 and 6, FIG. 1)).
Here, for fixing the rod lens array on the lens holder, the rod lens array must be fixed while maintaining highly precise straightness. Therefore, the rod lens array is fixed on the lens holder by using an adhesive (e.g., UV adhesive) that is adherable in a short period of time, while straitening the rod lens array using a jig that has a rod lens array contact surface with a high degree of straightness.
However, in the exposure device with the above-described configuration, there are cases where the rod lens array warps toward the photosensitive drum and where the adhesive between the lens holder and the lens array peels, when the exposure device is left in a high temperature environment. As a result, print quality may be decreased because the image forming condition of the light with respect to the photosensitive drum changes and thereby good electrostatic latent images are not obtained.